Horizontal swan-neck robots, also known as SCARA (Selective Compliance Robot Arm), are commonly used as manipulators for substrate transport or for assembly tasks. Usually, such manipulators have to carry quite heavy loads, and also, each of their axes usually need to be motorised, the motor often placed at the joints. As a consequence, the entire construction is heavy and therefore needs to be very stiff in order to support the load, as each axis contains its own motorisation and the payload effects at the end of the arm. This is the reason the known solutions are bulky and short.
The main disadvantage in applying the SCARA principle for measuring machines is its bulkiness, the limited probe accessibility, its equipment with motors along the arms, the resulting heaviness, its high moment of inertia, the heat generation, the limited accuracy resulting from said disadvantages as well as restricted dynamic behaviour.
The substrate transporting robot shown in US 2007/0020082 A1 presents a solution to shift the heavy motors of such arms into the pillar of the robot to avoid causing high momentum bearing on the arms.
The antenna testing robot known from U.S. Pat. No. 6,354,167 is inspired from arm-type drafting machines which are a solution known from the era prior to CAD software. Disclosed therein is a torque transmission for moving the probe placed at the end of the arm.
The present invention is based on an evolution of the stated SCARA technology while being carried over into the field of high precision coordinate measuring machines.